Kenyan dominance of men's middle and long-distance running has become a fact of life since the 1988 Seoul Olympics.
One explanation for their supremacy enters one of sport's most sensitive arenas.
According to Professor Bengt Saltin of Copenhagen University, who has devoted more than 30 years to studying muscle biology, the east Africans have inbuilt advantages.
In a documentary film "Race for Kenya", Saltin said he had studied young, sendentary Kenyans.
"We saw that when it comes to some features of the muscle they were, already, as young teenagers different from, for example, Europeans as well as Nigerians," Saltin said.
"Another area equally interesting is that the muscle produces what we call metabolites when it exercises, hard lactic acid for example which is a fatigue factor.
"It also produces ammonia in large amounts when it's really pushed to the extreme. And the Kenyan runners, they don't produce ammonia during very intense work. In fact when they run at maximum speed they have the same ammonia concentration as European top runners at rest."
"So these are the type of indications saying there is quite likely a genetic component."
Other experts prefer to look at the Kenyans' renowned work ethic.
"From a cultural point of view, they live in a much tougher culture than we do," said athletes' agent Kim McDonald. "This is the opportunity, this is their equivalent of the NBA.
"They see if they train hard and compete well on the world stage that means they earn money and that money buys land and housing, construction, cars, sends their brother and sisters to school."
Altitude training is another theory advanced for Kenya's hegemony and many of the world's top long-distance athletes now retreat to thin mountain air to increase their bodies' capacity to utilise oxygen at sea level.
Here again there are dissenting views, notably from Moses Kiptanui, the finest steeplechaser ever.
"Despite the fact that I was born in high altitude, I don't think it has contributed to my success," said Kiptanui. "If we recall the 1980s, England had their good athletes like Sebastian Coe, Steve Cram, (Steve) Ovett. They were born in low altitude and they were training in low altitude and they were running world records."
An issue raised by those who oppose the genetic argument is the comparative lack of success for Kenyan women.
Saltin has an answer.
"There's no question Kenyan women have at least the same potential as men," he said. "It just that society prohibited them in earlier decades from developing that talent."
Ank de Vlas, head teacher at Kapkenda Girls' High School agrees.
"When they're in school they can do a lot of running, they can do a lot of practising in whatever clothes they want to wear," De Vlas said. "But when they're growing up the culture actually refuses them to run in running shorts and things like that.
"So that once a girl gets to the age of 17, 18, when the sexual ideas are coming up, the men refuse to marry the girls if they are running around, as they say, half-naked. We are now trying to bite through that one and I think we are winning."
Saltin rejects any suggestion that his researches are racially motivated.
"People think we are doing this to find racial or ethnic difference and of course we're not doing it for that at all," he said. "We just want to find out what makes a good runner.
"We see more of a difference, for example, between Nigerians and East Africans. And the East Africans, in some respects, are more similar to the Europeans. So I don't think there should be any tensions about a subject like that."